1. Field of the Invention
Aromatic carboxylic acids of the type of the formula ##STR3## or their acid chlorides and esters are particularly useful intermediates in the polymer sector and are suitable, for example, as monomers for the preparation of polyesters, polyester carbonates or polyamides, having a high heat resistance.
2. Description of the Related Art
Only a few representatives of this type are known, however, owing to the poor accesibility. Thus, in U.S. Pat. No. 2,794,822 the preparation of 2,2-bis-(p-carboxyphenyl)-propane by the following processes is described: Firstly, acetone is reacted with phosphorus pentachloride to give 2,2-dichloropropane (27% yield), which reacts further with benzene in the presence of aluminum chloride to give 2,2-diphenylpropane (46%). This hydrocarbon was then doubly acetylated in the para, para-position with acetyl chloride and aluminum chloride (56%) and the diacetyl product was oxidized with sodium hypochlorite to give 2,2-bis-(p-carboxyphenyl)-propane as the aromatic dicarboxylic acid (89%). The other route described therein, also starting from 2,2-dichloro-propane, leads with toluene in the presence of aluminum chloride to 2,2-bis-(p-tolyl)-propane and oxidation of this with nitric acid in the presence of ammonium vanadate as catalyst leads to the aromatic dicarboxylic acid mentioned. A still further route described in U.S. Pat. No. 2,794,822 leads via the condensation of acetone with aniline to 2,2-bis-(p-aminophenyl)-propane, which is reacted with the aid of sodium nitrite and cyanid ions to give the corresponding dinitrile, which is then hydrolyzed with acid to give the aromatic dicarboxylic acid mentioned.
The processes mentioned proceed with poor yields and are based on the use of poorly accessible geminal dichlorides or highly toxic intermediates and are therefore little suited for industrial application. The processes are additionally greatly restricted with respect to their width of application to homologous compounds.